Apparatus for treating granular material

ABSTRACT

Apparatus for cleaning granular material such as foundry sand and the like comprises a housing having upstanding tubular inner and outer walls in spaced apart coaxial relation defining an annular receiving chamber adjacent the lower end for holding granular material to be cleaned, annular plenum chamber means below said receiving chamber having an upper wall forming a base of said chamber and supporting a plurality of spaced apart injection nozzles for directing high velocity air flow upwardly into the granular material to lift the same via lift tubes having their lower ends coaxially aligned with and spaced above said nozzles for carrying an upward flow of airborne granular material for impacting against target means spaced above said inner wall, outlet means defined in said outer wall for removing from said housing airborne fine particles of material obtained after impact of said material against said target means and adjustable gate means below said target means for directing a flow of clean base particles of granular material through said inner wall for discharge.

United States Patent [191 Kauffman July 23, 1974 APPARATUS FOR TREATING GRANULAR [57] ABSTRACT MATERIAL Apparatus for cleaning granular material such as [75] Inventor; John Kauffman, Richland foundry sand and the like comprises a housing having Center, Wis. upstanding tubular inner and outer walls in spaced apart coaxial relation defining an annular receiving Asslgneei Nalional Engineering Company, chamber adjacent the lower end for holding granular Chlcago, material to be cleaned, annular plenum chamber [22] Filed; 14, 1973 means below said receiving chamber having an upper wall forming a base of said chamber and supporting a 1 PP N05 332,415 plurality of spaced apart injection nozzles for directing high velocity air flow upwardly into the granular mate- 52 us. Cl. 241/40, 241/1310. 10 rial to lift the Same via lift tubes having their lower 51] Int. Cl. B02c 19/06 ends coaxially aligned with and Spaced above Said 1101- 5 Field f S 241/39 40 41 42 10 Zles for carrying an upward flOW Of airborne granular material for impacting against target means spaced 5 References Cited above said inner wall, outlet means defined in said UNITED STATES PATENTS outer wall for removing from said housingairborne fine particles of material obtained after impact of said 2 5 3? material against said target means and adjustable gate 2I939Il89 6/1960 winning :II:...............::I: z1/40 x means'below Said target means for directing a flow of Primary ExaminerGranville Y. Custer, Jr.

' clean base particles of granular material through said inner wall for discharge.

l 14 Claims, 6 Drawing Figures as 88 ea 2 8 I2 WENIEBJumIBM SHEET 10F 3 AWTH HWH PMENTED JULZ 3 I974 SHEET 2 OF 3 APPARATUS FOR TREATING GRAAR MATERIAL The present invention relates to a new and improved apparatus for treating granular material and more particularly to new and improved apparatus for reclaiming for reuse the granular materials commonly used in foundry operations such as foundry sand and the like. The present invention is an improvement over the apparatus shown and described in U.S. Pat. No. 3,088,183 and assigned to the same assignee as the present invention.

In foundry operations granular base materials such as silica sand, zirc'onia sand and the like are coated with binding products, for example, clays, cereals, resins, and oils and the resulting mixture comprises foundry sand which is shaped and molded into definite shapes around patterns to form mold cavities. Molten metal is poured into the cavities as castings are made. The green molding sand is subjected to direct contact with hot molten metal and the binding products which coat the granular sand base materials are oxidized and/or calcined in the process of molding. In order to recondition the base material for further use in'foundry operations, it is desirable to remove the oxidized coatings from the basic sand granules and subsequently prepare the sand as molding sand in suitable formulations with the necessary binding products required for a mold. The oxidized or calcined coating materials on the used molding sand granules are generally carbonaceous in nature and also are of a generally lower density than the basic sand material itself.

Accordingly, it is desirable to provide a system for removing the encrusted coating material from the sand grains in a dry mechanical process and subsequently separate the lighter weight materials from the basic sand so that the clean sand may then be reused after reformulation with the necessary binders. The apparatus of the present invention is adapted to be a selfcontained, relatively inexpensive unit requiring a relatively small floor space package and capable of adjustment to meet different desired time periods of scrubbing/cleaning action as may be required by the particular granular material being treated.

It is therefore an object of the present invention to provide a new and improved apparatus for treating granular materials such as foundry sand and the like, and more particularly it is an object of the invention to provide a new and improved apparatus of the character described which is highly efficient in operation, is relatively inexpensive, and which requires a relatively small floor space per unit of capacity in comparison with prior sand scrubbers.

Another object of the present invention is to provide a new and improved apparatus for treating granular material of the character described including a unitary housing adapted to contain and enclose a plurality of separate individual mechanical impact type sand scrubbing units.

Another object is to provide apparatus of the character described which is readily adapted for the addition .of more scrubber units as required when capacity of the apparatus is to be increased.

Another object of the present invention is to provide a new and improved apparatus for treating granular material having a novel target system for receiving the impact of flowing granular material in order tome chanically remove the calcined or oxidized coatings from the basic sand granules.

Another object of the invention is to provide a new and improved dry process, mechanical. impact type sand scrubber of the character described which scrubber requires a minimum amount of horsepower yet obtains cleaning results comparable or better than that of prior scrubbers.

Another object of the present invention is to provide a new and improved apparatus for treating granular material and the like readily adapted to treat different size batches of material for selectively adjustable different time period of scrubbing operation.

The foregoing and other objects and advantages of the present invention are accomplished in an illustrated embodiment by-way of illustration and not limitation comprising a dry process mechanical impact type sand scrubber system including a unitary housing having upstanding tubular inner and outer walls in spaced apart coaxial relation defining an annular receiving chamber adjacent the lower end for receiving the granular material to be cleaned. Annular plenum chamber means is provided below the receiving chamber and the chamber means has an upper wall forming a base of the receiving chamber supporting a plurality of spaced apart air injection nozzles for directing high velocity air jets upwardly into the granular material tolift the same. Above each nozzle is provided a lift tube having its lower end aligned with and spaced above the nozzle for carrying the upward flow of airborne granular material for impacting against target means spaced above the upper end of the inner housing wall. Impacting of the material against the target means causes the calcined and/or oxidized lighter weight materials coating the sand granules to break away and these lighter weight fines are carried upwardly in the air flow for discharge through an outlet means at the upper end of the housing. The heavier, clean sand grains and the grains 0r granules still having some coating materials encrusted thereon gravitate downwardly towards the receiving chamber for further impact treatment until substantially all of the coating material on the sand grains has been removed. Adjustable gate means is provided below the target means for directing a flow of cleaned materialsout of the housing for discharge via the lower end of the inner wall of the housing.

For a better understanding of the invention reference should be had to the following detailed description taken in conjunction with the drawings, in which;

FIG. 1 is an elevational view of a new and improved apparatus for treating granular material constructed in accordance with the features of the present invention with portions thereof shown in sections for clarity;

FIG. 2 is a transverse horizontal cross sectional view taken substantially along lines 2-2 of FIG. 1;

FIG. 3 is a vertical sectional view of a second embodiment of a new and improved apparatus for treating granule material constructed in accordance with the features of the present invention;

FIG. 4 is a transverse cross sectional view taken substantially along lines 44 of FIG. 3;

FIG. 5 is a vertical sectional view of a third embodiment of a new and improved apparatus for treating granule material constructed in accordance with the features of the present invention; and

FIG. 6 is a transverse cross sectional view taken substantially along lines 66.

Referring now more particularly to the drawings in FIGS. 1 and 2 is illustrated a novel apparatus for treatment of granular material such as foundry sand and the like constructed in accordance with the features of the present invention and referred to generally by the reference numeral 10. The scrubber includes a cylindrical housing 12 having a tubular upstanding outer wall or shell 14 formed with stiffening angle ring flanges 16 at the upper and lower ends. The outer shell 14 is adapted to rest on the upper end of a supporting hopper structure 18 which receives the cleaned sand processed by the scrubber and a clean sand hopper 19 holds the sand for discharge eventually onto a conveyor or other conveyance not shown.

The lower hopper system 18 comprises an upstanding tubular wall 20 having stiffening angle ring flanges 22 at the upper and lower ends. The lower flange 16 of the scrubber housing 12 is attached to the upper ring flange 22 of the clean sand hopper and the lower ring flange 22 of the hopper is adapted to be attached to a floor or other supporting surface for anchoring the whole scrubber system in place.

The hopper wall 20 is provided with one or more enlarged rectangular openings 24 in order to provide access to a sand discharge outlet 26 formed at the lower end of a frustroconical hopper bottom wall 28. The discharge outlet 26 is controlled with a movable valve 30 (dotted lines, FIG. 1) so that a quantity or batch of clean sand may be accumulated in the hopper 19 until ready for discharge when the valve is opened to flow onto a conveyor or other conveyance. Upper portions of the hopper wall 20 may be provided with larger generally rectangular access openings 32 normally covered or closed by removable cleanout doors 34. The openings provide access to the interior of the hopper 19 as required.

At the upper end of the scrubber housing wall 14 there is provided a scrubber support section 36 having a peripheral wall comprising the web of a rolled channel iron ring 38. The lower flange of the channel 38 is secured to the upper flange ring 16 on the housing wall 14 and a plurality of transverse support beams 40 extend radially outward from a central point on vertical axis of the scrubber housing 12. The support beams are connected at their outer ends to the web of the channel ring 38.

In order to supply sand or other granular material to the scrubber for cleaning there is provided an upper supply housing 42 having an upstanding outer cylindrical wall 44 with an angle ring flange 46 at the lower end secured to the upper flange of the channel ring 38. A frustroconical wall forms a bottom of a supply hoppper 49 holding a batch or quantity of dirty sand to be cleaned. Sand is discharged from the lower end of the hopper through a discharge chute 50 attached at the lower end of the frustroconical bottom 48. Sand or other granular material to be processed in the scrubber 10 is fed into and stored in the upper end of the supply hopper 49 and flows downwardly for controlled discharge via the discharge chute 50. A conical baffle 52 is mounted in the hopper in coaxial alignment above the upper end of the discharge chute to prevent clogging thereof. The baffle is supported by a plurality of radially extending ribs 54 joined at their outer ends to the frustroconical hopper bottom wall 48.

In order to selectively control the discharge of sand or other granule material from the hopper 49, a frustroconical valve 56 is mounted below the outlet end of the discharge chute 50 for vertical movement toward and away from the lower end. The valve member 56 is mounted on the upper end of the piston rod 58 of a valve control, vertical fluid cylinder 60 coaxially aligned with the central axis of the scrubber and supported by the beams 40.

In accordance with the present invention, air flow for moving the sand or other material particles to be cleaned into impacting engagement with target means for removing encrusted materials from the sand grains is introduced into the lower end of the scrubber housing 12 via an inlet duct 62. Air is exhausted from the upper housing section 42 along with the fines consisting of coating materials that are removed from the sand grains through an outlet duct 64 spaced below the outer edge of the conical hopper bottom wall 48. A fan or blower (not shown) is used for moving the air through the system at the desired pressure and volume flow rate and the blower preferably is connected on the pressure side of the system to direct a stream into the inlet duct 62. A suction fan connected on the outlet duct 64 may also be used to move the air through the system. Air from the inlet duct 62 passes into an annular plenum chamber 66 formed at the lower end of the scrubber housing 12. The scrubber is provided with an upstanding cylindrical inner wall 68 having an open lower end in communication with the clean sand hopper 19. The inner wall 68 and the outer housing wall 14 define an annular receiving chamber 70 adjacent the lower end of the housing above the plenum chamber 66 and separated therefrom by an annular wall 72. The lower end of the plenum chamber is closed by an annular bottom wall 74 to complete an annular enclosure forming the supply plenum chamber 66 for the system. Gas is directed upwardly from the plenum chamber at high velocity through a plurality of circumferentially spaced apart tubular convergent flow nozzles 76. The nozzles are mounted in circular openings formed in the annular upper wall 72 of the plenum as best shown in FIG. 2 and preferably are spaced at equal intervals from one another. I-Iigh velocuty air flow from the nozzles 76 into sand contained in the receiving chamber 70 picks up the material in upwardly directed airborne streams of high velocity. The airborne flow of material in each stream enters an inlet fitting 78 on the lower end of a vertical flow tube 80 coaxially aligned with the axis of each nozzle and supported from the upper end by a beam 40. The flow tubes 80 hang in vertical position above the nozzles and are supported by means of adjustable I-bolts 82 and cables 84 interconnected to hangars 85 welded or otherwise attached to the upper end of the flow tubes. The cables 84 may be shortened and/or lengthened therein to adjust the vertical spacing between the lower end of the inlet fittings 72 and the upper ends of the respective flow nozzles 76 aligned therewith. The amount of spacing between each nozzle and inlet fitting is adjusted to provide a desired feed rate of material into the lift tube at a particular air flow volume and for a particular type of material.

In accordance with the present invention, each lift tube 80 is formed with a closed upper end wall 86 and a right angle discharge conduit 88 spaced below the upper end wall. During operation the space between the end wall 86 and the lateral discharge conduit 88 in each lift tube is filled with material which forms a sort of sand pad against which the upwardly stream of material is impacted. The conduits 88 are all directed to disimpacts directly against the sand pad formed below the upper end wall 86 and then falls downwardly to the level of the right angle discharge conduits 88. The downwardly falling material is impacted by the upwardly moving material and an intense impact zone is developed within the upper end portion of the flow tubes 80 adjacent the level of the lateral discharge conduits 88. Very little wear on the end wall 86 occurs because of the sand pad that is formed. The sand then flows radially inwardly toward the center of the scrubber housing and is discharged from the conduits at a level spaced above the upper end of the inner cylindrical wall 68. 7

As best shown in FIG. 2, the horizontal discharge conduits 88 are aligned in diametrically opposed pairs so that the material flowing inwardly and discharged from one conduit is directed against the'material dis-- charged from an opposite conduit. The opposing streams of material form targets for one another and as the granules impactagainst those discharged from the opposite direction, the coating material on the granules is broken off and carried away by the air stream as fine material.

The impact region of the intersecting and opposing flow of granular'material from the discharge conduits 88 takes place above the center of the inner housing wall 68. As the particles or granules of granular material impact upon one another in this region any coatings of oxidized or calcined material remaining on the sand grains is broken off and because these broken off coating materials are relatively light in weight in comparison withthe sand grains, they are buoyed upwardly by the flow of air in the housing and pass out via the outlet duct 64. The heavier, more dense sand grains and especially those granules on which the coating has remained in tact gravitate downwardly from the impact region or zone at the center of the scrubber housing and flow onto a conically shaped roof wall 89 which closes off the upper end of the inner wall 68 of the housing. The material gravitating back into the lower: end of the annular receiving chamber 70 between the inner wall 68 and the lower end portion of the outer wall 14 is again carried upwardly by the high velocity air streams issuing from the nozzles 76 and moves via the lift tubes 80 and right angle discharge conduits 88 to the central impact zone. The crust or coating material on the sand grains is thus subject to impact breakage against the end walls 86 of the lift tubes 80 followed by impact against upwardly flowing sand granules at the level of the discharge conduits 88 and finally is subjected to a third impact zone at the center of the housing developed by the discharge of the granule streams from opposing conduits 88.

After a long enough period of time has elapsed, substantially all of the coating material on the sand grains has been broken off by impact against the end walls 86 or with other grains in the central impact zone. This fine material is carried out of the housing on the exhaust air stream via the outlet duct 64. The heavier,

' more dense clean sand granules flow downwardly over the conical roof 89 and return by gravity to the lower end of the receiving chamber 70. Returning granules are continuously recycleduntil the sand-grains appear to have all the unwanted coatings or crust materials removed. Normally the scrubber 10 is operated on a batch basis, wherein a given volume of granular material to be cleaned is introduced into the scrubber by opening of the valve 56 for a timed interval corresponding to the desired batch or charge size desired. Air flow is continuous during the charging to prevent the flow of material into the plenum chamber 66. After the charging cycle is completed, repeated impacting of the material is continued in the manner aforesaid for a selected time interval until substantially all of the carbonaceous, calcined or oxidized coating materials on the grains are removed and carried away out of the scrubber housing through the outlet section 64.

The lift tubes are adjusted to maintain precise coaxial vertical alignment with the respective nozzles 76 by means of adjustable length strut assemblies 90 which extend between the inner wall 68 and outer wall 14 of the scrubber housing adjacent the lower end. Upper strut assemblies are provided to extend between the conical roof section 89 and the outer wall of the housing'adjacent the upper end of the lift tubes.

After sufficient impact scrubbing action on the granules has been completed, the cleaned sand grains are discharged from the scrubber housing 12 into the clean sand supply hopper 19 in preparation for the next batch of material'to be cleaned. For this purpose, the inner wall 68 is provided with a plurality of circumferentially spaced openings 92 adjacent the lower end and each opening is provided with a discharge door 94 preferably formed from the wall material after it is cut from the wall to provide the openings. The doors are hingedly attached along their upper edge to the upper edges of the discharge openings for movement between an upright, closed position sealing off the openings and downwardly and inwardly sloped, open position (as shown) for discharge of the material flowing downwardly over the edge of the conical roof 89 and discharged through the openings 92 into the interior of the inner housing wall 68. With the doors closed the material is continuously recycled as long as air flow is supplied and after cleaning is completed the doors are opened and the material is discharged. During a discharge cycle, all the material which does not pass through an open door is recycled and recycling continues until substantially all of the material in the housing 12 has been discharged through the openings 92. After a discharge cycle is completed a small volume of material may still remain on the floor 72 of the chamber 70. This volume is dependent on the angle of repose of the material and is relatively small as indicated by the dotted lines. Preferably the outlet end of each air nozzle 76 is at a level above the angle of repose so that when the air flow to the plenum chamber is discontinued, little if any material will flow through the nozzle passages into the plenum 66. Accordingly, restarting of a scrubbing cycle after shut down of the air flow does not require compressed air to clean out the plenum 66 and removable mechanical plugs for the nozzles are not normally required.

The lower end of the inner wall 68 is open and in direct communication with the upper end of the clean sand hopper 19 so that material passing through the discharge openings 92 when the doors 94 are opened falls directly into the hopper. Movement of all of the doors 94 in unison between an upright closed position and a range of open positions at any selected slope angle is accomplished by a single door cylinder 96 mounted under the conical roof 89 in coaxial vertical alignment with the center axis of the housing. The cylinder is supported from a spider structure 97 and a rod 98 of the cylinder is pivotally connected at its lower end with a plurality of outwardly extending door control links 99 pivotally connected to the inside of the respecting discharge doors 94. When the cylinder rod 98 is fully extended in a downward direction the doors are pivoted to the upright, closed position and are normally retained in this position during the scrubbing period. After sufficient scrubbing has'taken place the rod 98 is retracted into the cylinder 96 and the doors 94 are pivoted to open and discharge the flow of material from the edge of the conical roof through the openings 92 into the interior of the inner housing wall 68 to fall into the clean sand hopper 19.

As illustrated in FIG. 2 the sand scrubber 10 includes at least one pair of diametrically oppositely spaced scrubbing units, each unit having an elbow section directed toward that of the opposite one. As indicated by the dotted lines, additional diametrically spaced pairs of scrubbing units may be added as required for increased capacity, and this may be accomplished without an increase in the housing size or floor space required. Each scrubbing unit including a convergent nozzle 76, an inlet fitting 78, and a lift tube 80 in coaxial alignment and a right angle discharge conduit 88 operates in parallel with other scrubber units in the scrubber housing and each additional pair of scrubber units added to the housing increase the capacity of the scrubber and reduce the time required for cleaning a batch of material of a given size.

As wear occurs in the high abrasion areas adjacent the lower end of the lift tubes 80, th inlet fittings 78 may be replaced and between replacement as wear occurs the spacing distance between the nozzles 76 and inlets which spacing regulates the flow rate of material into the lift tubes may be maintained substantially constant by changing the length of the cables 84 which support the tubes from the upper support beams 40.

Referring to the embodiment of FIGS. 3 and 4, a scrubber 110 is therein illustrated which is similar or identical in many aspects to the previously described embodiment. Identical reference numbers are used to identify components of the scrubber 110 which are the same as those of the scrubber l0 and only the differences between the two scrubbers will be pointed out herein in detail. In the scrubber 10, the target means for the impact scrubbing of the granules in the flow of airborne sand or granular material comprises the interaction between the particles of material impacting against one another in the flow tube adjacent the upper end and the impacting against the end walls 86 as well as the impacting of particles against one another when discharged from the conduits 88 in opposing streams. The impact region in the flow tubes 80 prevents most of the wear on the end walls 86 and the final impact region is centered above the conical roof 89 thus requires no physical structure as the material itself provides its own target means.

In the scrubber 110 a target 100 is provided above the apex of the conical roof 89 and the target is supported by I-bolts 82 and cables 84 from the beams 40 in a manner similar to arrangement for supporting the lift tubes 80 as previously described. The target 100 is constructed from a plurality of concave impact hoods 101 clustered together and arranged with concave impact surfaces 102 centered and in direct facing relation with the outlet end of the respective conduits 88. The hoods 101 are similar or identical in shape to those shown in the aforementioned US. patent incorporated herein by reference. The airborne material issuing from the conduits impacts the surfaces 102 of the hoods 101 and the encrusted coating material on the grains is broken off. The scrubber 110 thus provides a physical target 100 as the final stage of impact scrubbing.

As in the prior embodiment, the heavier clean sand and material gravitates downward onto the roof 89 for recycling until discharge while the lighter weight fine particles are carried upwardly by the air flow and are moved out of the housing via the outlet duct 64. The target 100 and its individual hoods 101 can be replaced or repaired from time to time as wear occurs because of the abrasive impact action of the flowing particle streams. However, the concave surfaces 102 of the target form and hold a pad or cushion of sand grains against which the discharging streams are directed and accordingly little wear of the target metal occurs.

Referring to FIGS. 5 and 6, therein is illustrated yet another embodiment of the invention comprising a scrubber 210 wherein each scrubbing unit is provided with an individual target hood 212. Again identical reference numbers will be used for components of the scrubber 210 similar or identical to those of the prior embodiments and only the differences will be described herein in detail. The scrubbing unit assemblies comprise the nozzle 76, inlets 78, lift tubes 80 and the target hoods 212 are similar to those shown and described in the aforementioned US. patent.

Because interaction between oppositely positioned scrubbing units is not a requisite as is also the case in the scrubbing units of the scrubber 110, any number of units, odd or even can be provided in the housing (within space limits) to achieve the desired capacity. In the scrubber 210, the lift tubes 80 are open at the upper end (no right angle discharge conduits 88 being provided) to direct the airborne flow of material for impact against the sand pads held and formed on the underside of coaxially aligned target hoods 212. The hoods are generally conical in shape with a cylindrical lip around the lower periphery as shown. Each scrubber unit is supported by its target hood 212 from an I- bolt 82, cable 84 and hangar 86 integrally formed on the upper surface of the hood. Each hood includes a pair of ears 214 and a pair of L-shaped arms 216 depending therefrom for supporting a coaxial ring 218 into which the upper end of a lift tube 80 is inserted and secured to provide precise coaxial alignment. The material striking the sand pad of each hood is deflected downwardly and the heavier material gravitates back to the lower end of the receiving chamber or passes through the open discharge doors 94 during a discharge cycle while the lighter weight fine material is carried upwardly by the buoyant air flow and discharged from the housing.

As the present invention has been described by reference to several embodiments thereof, it will be apparent that numerous other modifications and embodiments will be devised by those skilled in the art which will fall within the true spirit and scope of the present invention.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. Apparatus for impact cleaning of granular material such as foundry sand and the like comprising a housing having a pair of upstanding tubular inner and outer side walls in spaced apart coaxial relation defining an annular receiving chamber adjacent the lower end for holding granular material, annular plenum chamber means below said receiving chamber supporting a plurality of spaced apart injection nozzles for directing high velocity air streams upwardly into said granular material in said receiving chamber'to lift the same, at least one pair of lift tubes spaced on opposite sides of said inner wall, and a laterally extending discharge conduit adjacent the upper end portion of each lift tube for directing the airborne flow of material therein inwardly toward target means in said housing above said inner wall, said lateral discharge conduits of each lift tube'of a pair of said lift tubes being aligned to discharge said airborne flow of material toward the discharge of flow from the opposite discharge conduit, each lift tube having a lower end coaxially aligned with and spaced above each nozzle for receiving an upward flow of airborne material, outlet means adjacent the upper end of said housing for removing from said housing airborne fine particles of material removed from said granular material by impact against said target means, and discharge gate means below said target means for directing a flow of cleansed particles of said granular material from said housing.

2. The apparatus of claim 1 including sloped roof means on the upper end of said inner wall for directing the heavier material discharged from said lateral discharge conduits downwardly and outwardly toward said receiving chamber.

3. The apparatus of claim 1 including target means in the center of said housing above said inner wall having concave surfaces thereon facing the discharge of said lateral discharge conduits.

4. The apparatus of claim 2 including a discharge opening defined in said inner wall below the upper end thereof, said discharge gate means including at least one door means hingedly attached along a lower edge to said inner wall for opening and closing said discharge opening.

5. The apparatus of claim 4 wherein said inner wall is formed with a plurality of circumferentially spaced apart discharge openings therein in communication between the interior thereof and said receiving chamber, said gate means including a door hingedly secured adjacent each opening movable between a closed position and an open position for directing material from said housing, and control means for opening and closing said doors simultaneously.

6. Apparatus for cleaning granular material such as foundry sand and the like comprising an upright housing, means for introducing material to be cleaned into the upper end of said housing, discharge means for removing cleaned material from the lower end of said housing, lift means for introducing a high velocity air flow into the material in the lower end of said housing for elevating the same in a plurality of separate steams for impact against target means to remove coating material therefrom, and means for removing air and coating material carried thereby from the upper end of said housing, said lift means comprising an annular plenum chamber adjacent the lower end of said housing includwall for discharge from said housing.

ing a plurality of upwardly directed nozzle outlets and lift tubes coaxially aligned therewith spaced circumferentially around said annular chamber, said discharge means comprising an upstanding tubular wall inside said housing in coaxial alignment therewith, said tubular wall extending upwardly of said plenum chamber and including closure means at the upper end and open at the lower end, a plurality of discharge openings in said tubular wall and a discharge door for each opening hingedly secured to an edge thereof for directing downwardly flowing material into the interior of said tubular 7. The apparatus of claim 6 wherein said discharge means includes a control linkage interconnecting said doors for simultaneously moving the same between upright positions, closed positions, and open positions wherein the lower edges of said doors are spaced inwardly of said inside tubular wall to direct material passing downwardly from said closure means into the interior of said tublar wall.

8. An impact scrubbing unit comprising an elongated tube open at an inlet end and closed at an opposite end, means for directing a high velocity flow of material to be scrubbed into said inlet end for passage toward said closed end, and means defining a lateral discharge opening in said tube for said material spaced from said closed end.

9. The impact scrubbing unit of claim 8 wheerin said means defining a lateral discharge opening includes an elongated discharge conduit angularly intersecting said lift tube and having an open outer end for discharging said material laterallyof said lift tube.

10. The impact scrubbing unit of claim 8 wherein said tube extends upwardly of said inlet end and said means defining a lateral discharge opening is spaced closely adjacent said closed end downwardly thereof whereby a pad of said material is collected and maintained between said closed end and said means defining said lateral discharge opening.

11. An impact scrubbing unit for removing coating material from the surfaces of granular materials such as foundry sand and the like comprising at least one pair of elongated tubes open at an inlet end and having discharge outlets in spaced apart opposing relation forming an impact scrubbing zone therebetween, injector means for carrying said granular material into the inlet ends of said tubes and providing a fluidized stream of said material at high velocity in said tubes for discharge from said outlets, said outlets positioned relative to one another whereby said fluidized material discharged from one of said tube outlets is directed to impact in said scrubbing zone against the fluidized material discharged from another outlet, and suction means for removing coating materials from said scrubbing zone while leaving said granular material.

12. The impact scrubbing unit of claim 11 wherein said tubes include discharge end portions in coaxial alignment having open discharge outlets in directly facing spaced apart relation.

13. The impact scrubbing unit of claim 12 wherein said tubes include upright sections having a closed upper end with said inlet end at the lower end thereof, said discharge end portion arranged to angularly intersect said upright sections at a position spaced below said closed upper end.

14. The impact scrubbing unit of claim 13 wherein said discharge end portions are horizontal and said upright sections are vertical. 

1. Apparatus for impact cleaning of granular material such as foundry sand and the like comprising a housing having a pair of upstanding tubular inner and outer side walls in spaced apart coaxial relation defining an annular receiving chamber adjacent the lower end for holding granular material, annular plenum chamber means below said receiving chamber supporting a plurality of spaced apart injection nozzles for directing high velocity air streams upwardly into said granular material in said receiving chamber to lift the same, at least one pair of lift tubes spaced on opposite sides of said inner wall, and a laterally extending discharge conduit adjacent the upper end portion of each lift tube for directing the airborne flow of material therein inwardly toward target means in said housing above said inner wall, said lateral discharge conduits of each lift tube of a pair of said lift tubes being aligned to discharge said airborne flow of material toward the discharge of flow from the opposite discharge conduit, each lift tube having a lower end coaxially aligned with and spaced above each nozzle for receiving an upward flow of airborne material, outlet means adjacent the upper end of said housing for removing from said housing airborne fine particles of material removed from said granular material by impact against said target means, and discharge gate means below said target means for directing a flow of cleansed particles of said granular material from said housing.
 2. The apparatus of claim 1 including sloped roof means on the upper end of said inner wall for directing the heavier material discharged from said lateral discharge conduits downwardly and outwardly toward said receiving chamber.
 3. The apparatus of claim 1 including target means in the center of said housing above said inner wall having concave surfaces thereon facing the discharge of said lateral discharge conduits.
 4. The apparatus of claim 2 including a discharge opening defined in said inner wall below the upper end thereof, said discharge gate means including at least one door means hingedly attached along a lower edge to said inner wall for opening and closing said discharge opening.
 5. The apparatus of claim 4 wherein said inner wall is formed with a plurality of circumferentially spaced apart discharge openings therein in communication between the interior thereof and said receiving chamber, said gate means including a door hingedly secured adjacent each opening movable between a closed position and an open position for directing material from said housing, and contrOl means for opening and closing said doors simultaneously.
 6. Apparatus for cleaning granular material such as foundry sand and the like comprising an upright housing, means for introducing material to be cleaned into the upper end of said housing, discharge means for removing cleaned material from the lower end of said housing, lift means for introducing a high velocity air flow into the material in the lower end of said housing for elevating the same in a plurality of separate steams for impact against target means to remove coating material therefrom, and means for removing air and coating material carried thereby from the upper end of said housing, said lift means comprising an annular plenum chamber adjacent the lower end of said housing including a plurality of upwardly directed nozzle outlets and lift tubes coaxially aligned therewith spaced circumferentially around said annular chamber, said discharge means comprising an upstanding tubular wall inside said housing in coaxial alignment therewith, said tubular wall extending upwardly of said plenum chamber and including closure means at the upper end and open at the lower end, a plurality of discharge openings in said tubular wall and a discharge door for each opening hingedly secured to an edge thereof for directing downwardly flowing material into the interior of said tubular wall for discharge from said housing.
 7. The apparatus of claim 6 wherein said discharge means includes a control linkage interconnecting said doors for simultaneously moving the same between upright positions, closed positions, and open positions wherein the lower edges of said doors are spaced inwardly of said inside tubular wall to direct material passing downwardly from said closure means into the interior of said tublar wall.
 8. An impact scrubbing unit comprising an elongated tube open at an inlet end and closed at an opposite end, means for directing a high velocity flow of material to be scrubbed into said inlet end for passage toward said closed end, and means defining a lateral discharge opening in said tube for said material spaced from said closed end.
 9. The impact scrubbing unit of claim 8 wheerin said means defining a lateral discharge opening includes an elongated discharge conduit angularly intersecting said lift tube and having an open outer end for discharging said material laterally of said lift tube.
 10. The impact scrubbing unit of claim 8 wherein said tube extends upwardly of said inlet end and said means defining a lateral discharge opening is spaced closely adjacent said closed end downwardly thereof whereby a pad of said material is collected and maintained between said closed end and said means defining said lateral discharge opening.
 11. An impact scrubbing unit for removing coating material from the surfaces of granular materials such as foundry sand and the like comprising at least one pair of elongated tubes open at an inlet end and having discharge outlets in spaced apart opposing relation forming an impact scrubbing zone therebetween, injector means for carrying said granular material into the inlet ends of said tubes and providing a fluidized stream of said material at high velocity in said tubes for discharge from said outlets, said outlets positioned relative to one another whereby said fluidized material discharged from one of said tube outlets is directed to impact in said scrubbing zone against the fluidized material discharged from another outlet, and suction means for removing coating materials from said scrubbing zone while leaving said granular material.
 12. The impact scrubbing unit of claim 11 wherein said tubes include discharge end portions in coaxial alignment having open discharge outlets in directly facing spaced apart relation.
 13. The impact scrubbing unit of claim 12 wherein said tubes include upright sections having a closed upper end with said inlet end at the lower end thereof, said discharge end portion arranged to angularly intersect said upright sections at a posItion spaced below said closed upper end.
 14. The impact scrubbing unit of claim 13 wherein said discharge end portions are horizontal and said upright sections are vertical. 